Fructose 2,6-bisphosphate. Hormonal regulation and mechanism of its formation in liver.
Vasopressin, phenylephrine, and A23187 cause an accumulation of fructose 2,6-bisphosphate in hepatocytes from fed rats, but not in Ca2+-depleted hepatocytes from fed rats or in phosphorylase kinase-deficient hepatocytes from (gsd/gsd) rats. The effect of vasopressin and phenylephrine is not found in hepatocytes from overnight-starved rats. Thus, the accumulation of fructose 2,6-bisphosphate by these agents may depend on the stimulation of glycogenolysis and on the resulting accumulation of hexose 6-phosphate. In support of this hypothesis, conditions are described for the enzymatic synthesis of fructose 2,6-bisphosphate from fructose 6-phosphate and Mg-ATP in liver extracts. Half-maximal activity (0.8 nmol/min.g) is obtained with about 60 microM fructose 6-phosphate, and the activity can be separated fom phosphofructokinase by ammonium sulfate fractionation. Treatment of rats or isolated hepatocytes with glucagon results in a 4-5-fold decrease in the maximal activity of this enzyme.
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D004789:Enzyme Activation; D005635:Fructosediphosphates / Q000378:metabolism*; D005934:Glucagon / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology; D006598:Hexosediphosphates / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology; D006005:Phosphorylases / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D014667:Vasopressins / Q000494:pharmacology*
D005635:Fructosediphosphates; D006598:Hexosediphosphates; D014667:Vasopressins; D010656:Phenylephrine; D000001:Calcimycin; C027652:fructose 2,6-diphosphate; D005934:Glucagon; D011433:Propranolol; D006005:Phosphorylases; D005947:Glucose